Laser driver with high-speed and high-current and integrated circuit thereof

ABSTRACT

A high-speed high-current laser driver integrated circuit is invented. The laser driver includes an input stage circuit, a pre-drive circuit, a negative capacitance circuit, three parallel-connected output stages, and an active reverse termination circuit. A pair of voltage signals V IP , V IN  are applied to the input stage circuit which amplifies these input signals to a pair of output voltage signals V IIP , V IIN . Then the voltage signals V IIP , V IIN  are amplified by the pre-drive circuit to a pair of voltage signals V + , V −  to the output stage circuit, and finally, a pair of modulated current signals I OP , I ON  are generated by the output stage circuit. The present invention does not use terminal resistance in the output stage circuit, so the power consumption of the circuit is much lower than that of the traditional circuit.

FIELD OF THE INVENTION

The present invention relates to the field of optoelectronic integratedcircuit (OEIC), in particular to a laser driver integrated circuit thatsimultaneously supports high-speed and high-current operation, and moreparticularly to a an integrated circuit.

BACKGROUND OF THE INVENTION

With the rapid development of communication networks, there is a highdemand for optical fiber communication networks with high bandwidth andlow loss. A laser driver is one of the key components in an opticalcommunication system as it controls the quality of the transmittedoptical signal. The driver circuit bandwidth and modulation current havesignificant impacts on the quality of the output optical signal. Inorder to work at high-speeds without inter-symbol interference (ISI),the laser driver must have sufficient bandwidth. In long-haulcommunication, the driver circuit must deliver high modulation currentto the laser diode for a large extinction ratio. Due to the mismatchbetween the laser's input impedance and the (printed circuit board)PCB's transmission line impedance, a termination network (such aspassive on-chip passive resistors) is usually required to absorb signalreflections from the laser side. If the terminal resistors and the inputresistance of the laser are perfectly matched with the characteristicimpedance of the transmission line, the reflected signal can becompletely absorbed. But half of the output current will be wastedthrough the terminal resistors, resulting in a large power waste.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a high-speed highcurrent laser driver integrated circuit to solve the problem of largepower consumption waste caused by using passive terminal resistors. Thisdesign does not use any passive back termination resistor, so the powerconsumption of the circuit is much lower compared to the traditionalcircuit. Another object of the present invention provides an integratedcircuit encapsulated by the laser driver with high-speed andhigh-current to avoid the large consumption waste.

The present invention provides a laser driver with high-speed andhigh-current, includes:

an input stage circuit;

a pre-drive circuit, being electrically connected to the out put ends ofthe input stage circuit;

a fully differential negative capacitance circuit, being electricallyconnected to the output ends of the pre-drive circuit;

a output stage circuit being electrically connected to the out put endsof the pre-drive circuit; and

an active reverse termination circuit; the input ends of the activereverse termination circuit being electrically connected to the inputends of the output stage circuit, and the output ends of the activereverse termination circuit being electrically connected to the outputends of the output stage circuit.

In the laser driver of the present invention, the active reversetermination circuit includes:

a pair of transistors M_(5A), M_(5B); the gate of the transistor M_(5A)is electrically connected to the positive output end of the pre-drivecircuit, the gate of the transistor M_(5B) is electrically connected tothe negative output end of the pre-drive circuit; the sources of thetransistors M_(5A), M_(5B) are electrically connected to a tail currentsource I_(M1)/k;

a pair of transistors M_(6A), M_(6B); the gate of the transistor M_(6A)is electrically connected to the positive output end of the pre-drivecircuit, the gate of the transistor M_(6B) is electrically connected tothe negative output end of the pre-drive circuit; the sources of thetransistors M_(6A), M_(6B) are electrically connected to a tail currentsource I_(M2)/k;

a pair of transistors M_(7A), M_(7B); the gate of the transistor M_(7A)is electrically connected to the positive output end of the pre-drivecircuit, the gate of the transistor M_(7B) is electrically connected tothe negative output end of the pre-drive circuit; the sources of thetransistors M_(7A), M_(7B) are electrically connected to a tail currentsource I_(M3)/k;

a pair of transistors M_(S1), M_(S2); the drains of the transistorsM_(5A), M_(6A), M_(7A) are electrically connected to the gate of thetransistor M_(S2), the drains of the transistors M_(5B), M_(6B), M_(7B)are electrically connected to the gate of the transistor M_(S1); thesource of the transistor M_(S1) is electrically connected to a tailcurrent source I_(B1), the source of the transistor M_(S2) iselectrically connected to a tail current source I_(B2);

a pair of resistors R_(3A), R_(3B); one end of these resistors isconnected with the drains of the transistors M_(S1), M_(S2) to a supplyvoltage V_(DD); the other ends of the resistors R_(3A) and R_(3b) areconnected to the gates of the M_(S2) and M_(S1), respectively; and

a pair of capacitors C₁, C₂; one end of the capacitor C₁ is electricallyconnected to the source of the transistor M_(S2), the other end ofcapacitor C₁ is directly connected to a output current terminal I_(OP);one end of the capacitor C₂ is electrically connected to the source ofthe transistor M_(S1), the other end of capacitor C₂ is directlyconnected to a output terminal I_(ON).

In the laser driver of the present invention, the input stage circuitincludes:

a transistor M_(D); the gate and drain of the transistor M_(D) areelectrically connected to the voltage source V_(DD);

a pair of transistors M_(1A), M_(1B); the gates of the transistorsM_(1A), M_(1B) respectively are used as the input ends of the inputstage circuit, the drains of transistors M_(1A), M_(1B) are electricallyconnected to input ends of the pre-drive circuit, the sources of theM_(1A) and M_(1B) are connected to a tail current source I₁; and

a plurality of resistors R_(INA), R_(INB), R_(1A), and R_(1B); one endof the resistor R_(INA) is electrically connected to a voltage sourceV_(CM), the other end of the resistor R_(INA) is electrically connectedto the gate of the transistor M_(1A); one end of the resistor R_(INB) iselectrically connected to the voltage source V_(CM), the other end ofthe resistor R_(INB) is electrically connected to the gate of thetransistor M_(1B); one end of the resistor R_(1A) is electricallyconnected to the drain of the transistors M_(1A), the other end of theresistor R_(1A) is electrically connected to the source of thetransistor M_(D); one end of the resistor R_(1B) is electricallyconnected to the drain of the transistors M_(1B), the other end of theresistor R_(1B) is electrically connected to the source of thetransistor M_(D).

In the laser driver of the present invention, both resistors R_(INA) andR_(INB) are 50 ohms.

In the laser driver of the present invention, the pre-drive circuitincludes:

a pair of transistors M_(2A), M_(2B); the gates of the transistorsM_(2A), M_(2B) are electrically connected to the drains of transistorsM_(1A), M_(1B) respectively, the drains of the transistors M_(2A),M_(2B) are electrically connected to input ends of the output stagecircuit, the sources of the transistors M_(2A), M_(2B) are connected toa tail current source I₂; and

a pair of resistors R_(2A), R_(2B); one end of the resistors R_(2A) isconnected to the drain of the transistors M_(2A), one end of theresistors R_(2B) is connected to the drain of the transistors M_(2B),the other ends of the resistors R_(2A), R_(2B) are connected to thevoltage source V_(DD).

In the laser driver of the present invention, the negative capacitancecircuit includes:

a pair of transistors M_(3A), M_(3B); the gate of the transistors M_(3A)and the drain of the transistors M_(3B) are electrically connectedtogether to the positive output end of the pre-drive circuit, the gateof the transistors M_(3B) and the drain of the transistors M_(3A) areelectrically connected together to the negative output end of thepre-drive circuit, the sources of the transistors M_(3A), M_(3B) areconnected to a pair of tail current sources I_(3A), I_(3B) respectively;and

a capacitor C_(c); two ends of the capacitor C_(c) are connected to thetail current sources I_(3A), I_(3B).

In the laser driver of the present invention, the output stage circuitincludes:

a pair of transistors M_(4A), M_(4B); the sources of the transistorsM_(4A), M_(4B) are electrically connected together to a tail currentsource I_(M1), the drains of the transistors M_(4A), M_(4B) representthe output ends of output current terminals I_(OP), I_(ON); the gate ofthe transistor M_(4A) is electrically connected to the positive outputend of the pre-drive circuit, and the gate of the transistor M_(4B) iselectrically connected to the negative output end of the pre-drivecircuit; and

a pair of transistors M_(CA), M_(CB); the source and drain of thetransistor M_(CA) are connected together to the output end of the outputcurrent terminal I_(ON), and the source and drain of the transistorM_(CB) are connected together to the output end of the output currentterminal I_(OP); the gate of the transistor M_(CA) is electricallyconnected to the positive output end of the pre-drive circuit, and thegate of the transistor M_(CB) is electrically connected to the negativeoutput end of the pre-drive circuit.

In the laser driver of the present invention, the output stage circuitis a three parallel connected output stages circuit.

In the laser driver of the present invention, the first output stage isdirectly connected to the output of the pre-drive circuit while thesecond and the third output stages are connected to the output ofpre-drive using switching circuits.

In the laser driver of the present invention, each switching circuitincludes:

a pair of transistors M_(S3), M_(S4); the gates of the transistorsM_(S3), M_(S4) receive a switch control signal V_(s), the sources of thetransistors M_(S3), M_(S4) respectively electrically are connected tothe inputs of the second output stage two input ends of thecorresponding switching circuit, the drains of the transistors M_(S3),M_(S4) are electrically connected to the output ends of the pre-drivecircuit respectively.

In the laser driver of the present invention, one of the witchingcircuits is controlled by a switch control signal V_(s1), and the otherof the switching circuits is controlled by a switch control signalV_(s2).

In the laser driver of the present invention, when the switch controlsignals V_(s1), V_(s2) are 0, the output modulation current can beadjusted from 10 mA to 50 mA; when the switch control signal V_(s1) is 1and the switch control signal V_(s2) is 0, the output modulation currentcan reach 100 mA; when the switch control signals V_(s1), V_(s2) are 1,the output modulation current is as high as 150 mA.

The present invention provides a laser driver with high-speed andhigh-current, includes:

an input stage circuit which receives a pair of fully differential inputvoltage signals, V_(IP), V_(IN), then, adjusting the common-mode outputvoltage of signals V_(IIP), V_(IIN), such that they could be applied tothe subsequent stage;

a pre-drive circuit, for amplifying the voltage signals V_(IIP), V_(IIN)to a pair of voltage signals V₊, V⁻;

a fully differential negative capacitance circuit that is directlyconnected to the output terminals of the pre-driver circuit, V₊, V⁻; thenegative capacitance circuit generates a negative capacitor to reducethe input capacitance of the output stage circuit;

an output stage circuit, for receiving the voltage signals V₊, V⁻, thenoutputting a pair of modulated current signals I_(OP), I_(ON); and

an active reverse termination circuit, for absorbing the reflected wavecaused by the output mismatch of the output stage circuit.

In the laser driver of the present invention, the active reversetermination circuit includes:

a pair of transistors M_(5A), M_(5B); the gate of the transistor M_(5A)receives the voltage signal V₊, the gate of the transistors M_(5B)receives the voltage signal V⁻; the sources of the transistors M_(5A),M_(5B) are electrically connected to a tail current source I_(M1)/k;

a pair of transistors M_(6A), M_(6B); the gate of the transistor M_(6A)receives the voltage signal V₊, the gate of the transistors M_(6B)receives the voltage signal V⁻; the sources of the transistors M_(6A),M_(6B) are electrically connected to a tail current source I_(M2)/k;

a pair of transistors M_(7A), M_(7B); the gate of the transistor M_(7A)receives the voltage signal V₊, the gate of the transistors M_(7B)receives the voltage signal V⁻; the sources of the transistors M_(7A),M_(7B) are electrically connected to a tail current source I_(M3)/k;

a pair of transistors M_(S1), M_(S2); the drains of the transistorsM_(5A), M_(6A), M_(7A) are electrically connected to the gate of thetransistor M_(S2), the drains of the transistors M_(5B), M_(6B), M_(7B)are electrically connected to the gate of the transistor M_(S1); thesource of the transistor M_(S1) is electrically connected to a tailcurrent source I_(B1), the source of the transistor M_(S2) iselectrically connected to a tail current source I_(B2);

a pair of resistors R_(3A), R_(3B); one end of these resistors isconnected with the drains of the transistors M_(S1), M_(S2) to a supplyvoltage V_(DD); the other ends of the resistors R_(3A) and R_(3b) areconnected to the gates of the M_(S2) and M_(S1) respectively; and

a pair of capacitors C₁, C₂; one end of the capacitor C₁ is electricallyconnected to the source of the transistor M_(S2), the other end ofcapacitor C₁ is directly connected to the output current terminalI_(OP); one end of the capacitor C₂ is electrically connected to thesource of the transistor M_(S1), the other end of capacitor C₂ isdirectly connected to the output terminal I_(ON).

In the laser driver of the present invention, the input stage circuitincludes:

a transistor M_(D); the gate and drain of the transistor M_(D) areelectrically connected to the voltage source V_(DD);

a pair of transistors M_(1A), M_(1B); the gates of the transistorsM_(1A), M₁, respectively receive the voltage signals V_(IP), V_(IN), theoutput voltage signals V_(IIP) and V_(IIN) are taken at the drains ofM_(1A), M_(1B) respectively, the sources of the M_(1A) and M_(1B) areconnected to a tail current source I₁; and

a plurality of resistors R_(INA), R_(INB), R_(1A), and R_(1B); one endof the resistor R_(INA) is connected to a voltage source V_(CM), theother end of the resistor R_(INA) is connected to the gate of thetransistor M_(1A); one end of the resistor R_(INB) is connected to thevoltage source V_(CM), the other end of the resistor R_(INB) isconnected to the gate of the transistor M_(1B); one end of the resistorR_(1A) is connected to the drain of the transistors M_(1A), the otherend of the resistor R_(1A) is connected to the source of the transistorM_(D); one end of the resistor R_(1B) is connected to the drain of thetransistors M_(1B), the other end of the resistor R_(1B) is connected tothe source of the transistor M_(D).

In the laser driver of the present invention, the pre-drive circuitincludes:

a pair of transistors M_(2A), M_(2B); the gates of the transistorsM_(2A), M_(2B) receive the voltage signals V_(IIP), V_(IIN)respectively, the drains of the transistors M_(2A), M_(2B) represent theoutput voltage signals V₊, V⁻ respectively, the sources of thetransistors M_(2A), M_(2B) are connected to a tail current source I₂;and

a pair of resistors R_(2A), R_(2B); one end of the resistors R_(2A) isconnected to the drain of the transistors M_(2A), one end of theresistors R_(2B) is connected to the drain of the transistors M_(2B),the other ends of the resistors R_(2A), R_(2B) are electricallyconnected to the voltage source V_(DD).

In the laser driver of the present invention, the negative capacitancecircuit includes:

a pair of transistors M_(3A), M_(3B); the gates of the transistorsM_(3A), M_(3B) receive the voltage signals V₊, V⁻, the drains of M_(3A)and M_(3B) receive the voltage signals V⁻, V₊ respectively, the sourcesof the transistors M_(3A), M_(3B) are electrically connected to a pairof tail current sources I_(3A), I_(3B) respectively; and

a capacitor C_(c); two ends of the capacitor C_(c) are electricallyconnected to the tail current sources I_(3A), I_(3B).

In the laser driver of the present invention, the output stage circuitincludes:

a pair of transistors M_(4A), M_(4B); the sources of the transistorsM_(4A), M_(4B) are connected together to a tail current source I_(M1),the drains of the transistors M_(4A), M_(4B) represent the output endsof the current signals I_(OP), I_(ON); the gate of the transistor M_(4A)receives the voltage signal V₊, and the gate of the transistor M_(4B)receives the voltage signal V⁻; and

a pair of transistors M_(CA), M_(CB); the source and drain of thetransistor M_(CA) are connected together to the output end of thecurrent signal I_(ON), and the source and drain of the transistor M_(CB)are connected together to the output end of the current signal I_(OP);the gate of the transistor M_(CA) receives the voltage signal V₊, andthe gate of the transistor M_(CB) receives the voltage signal V⁻.

The present invention also provides an integrated circuit, which isencapsulated by a laser driver with high-speed and high-current; thelaser driver includes:

an input stage circuit which receives a pair of fully differential inputvoltage signals, V_(IP), V_(IN), then, adjusting the common-mode outputvoltage of signals V_(IIP), V_(IIN), such that they could be applied tothe subsequent stage;

a pre-drive circuit, for amplifying the voltage signals V_(IIP), V_(IIN)to a pair of voltage signals V₊, V⁻;

a fully differential negative capacitance circuit that is directlyconnected to the output terminals of the pre-driver circuit, V₊, V⁻; thenegative capacitance circuit generates a negative capacitor to reducethe input capacitance of the output stage circuit;

an output stage circuit, for receiving the voltage signals V₊, V⁻, thenoutputting a pair of modulated current signals I_(OP), I_(ON); and

an active reverse termination circuit, for absorbing the reflected wavecaused by the output mismatch of the output stage circuit; wherein theactive reverse termination circuit comprises:

-   -   a pair of transistors M_(5A), M_(5B); the gate of the transistor        M_(5A) receives the voltage signal V₊, the gate of the        transistors M_(5B) receives the voltage signal V⁻; the sources        of the transistors M_(5A), M_(5B) are electrically connected to        a tail current source I_(M1)/k;    -   a pair of transistors M_(6A), M_(6B); the gate of the transistor        M_(6A) receives the voltage signal V₊, the gate of the        transistors M_(6B) receives the voltage signal V⁻; the sources        of the transistors M_(6A), M_(6B) are electrically connected to        a tail current source I_(M2)/k;    -   a pair of transistors M_(7A), M_(7B); the gate of the transistor        M_(7A) receives the voltage signal V₊, the gate of the        transistors M_(7B) receives the voltage signal V⁻; the sources        of the transistors M_(7A), M_(7B) are electrically connected to        a tail current source I_(M3)/k;    -   a pair of transistors M_(S1), M_(S2); the drains of the        transistors M_(5A), M_(6A), M_(7A) are electrically connected to        the gate of the transistor M_(S2), the drains of the transistors        M_(5B), M_(6B), M_(7B) are electrically connected to the gate of        the transistor M_(S1); the source of the transistor M_(S1) is        electrically connected to a tail current source I_(B1), the        source of the transistor M_(S2) is electrically connected to a        tail current source I_(B2);    -   a pair of resistors R_(3A), R_(3B); one end of these resistors        is connected with the drains of the transistors M_(S1), M_(S2)        to a supply voltage V_(DD); the other ends of the resistors        R_(3A) and R_(3b) are connected to the gates of the M_(S2) and        M_(S1) respectively; and

a pair of capacitors C₁, C₂; one end of the capacitor C₁ is electricallyconnected to the source of the transistor M_(S2), the other end ofcapacitor C₁ is directly connected to the output current terminalI_(OP); one end of the capacitor C₂ is electrically connected to thesource of the transistor M_(S1), the other end of capacitor C₂ isdirectly connected to the output terminal I_(ON).

In the integrated circuit of the present invention, the output stagecircuit is a three parallel connected output stages circuit; the firstoutput stage is directly connected to the output of the pre-drivecircuit while the second and the third output stages are connected tothe output of pre-drive using switching circuits; the pins of theintegrated circuit include:

a pair of input pins, for transmitting the voltage signals V_(IIP),V_(IN) to the input stage circuit;

a pair of output pins, which represent the output modulation current tothe laser diode;

a plurality of tail current source pins, for accessing the tail currentsources required by the driving circuit of the laser driver;

a plurality of voltage source pins, for accessing the voltage sourcesrequired by the driving circuit of the laser driver; and

two control signals pins, are used to activate the switching circuitsdesignated for the second and the third output driver stages.

A solution of the present invention, for solving the above problem, isthat the voltage signals V_(IIP), V_(IIN) are matched and adjusted bythe input stage circuit, and then amplified by the pre-drive circuit tothe output stage circuits. Finally, the output modulated current signalsI_(OP), I_(ON) are generated. The negative capacitance circuit is usedfor reducing the input capacitance of the output stage circuits. Theactive reverse termination circuit absorbs the reflected wave caused bythe output mismatch. There is no terminal resistance in the output stagecircuit, so the power consumption of the circuit is much lower than thatof the traditional circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore readily apparent to those ordinarily skilled in the art afterreviewing the following detailed description and accompanying drawings,in which:

FIG. 1 is a module diagram of the laser driver with high-speed andhigh-current when the number of the output stage circuit is only one,according to the embodiment of the present invention.

FIG. 2 is a circuit diagram of the laser driver with high-speed andhigh-current when the number of the output stage circuit is only one,and the active reverse termination circuit is not shown, according tothe embodiment of the present invention.

FIG. 3 is a circuit diagram of the active reverse termination circuit ofthe laser driver, according to the embodiment of the present invention.

FIG. 4 is a module diagram of the laser driver with high-speed andhigh-current when the output stage circuit is a three parallel connectedoutput stages circuit, according to the embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described more specifically withreference to the following embodiments. It is to be noted that thefollowing descriptions of preferred embodiments of this invention arepresented herein for the purpose of illustration and description only.It is not intended to be exhaustive or to be limited to the precisedisclosed form.

First Embodiment

Referring to FIG. 1, a laser driver with high-speed and high-current isshown. The laser driver with high-speed and high-current of the presentinvention includes an input stage circuit, a pre-drive circuit, a fullydifferential negative capacitance circuit, an output stage circuit andan active reverse termination circuit. The pre-drive circuit iselectrically connected to the out put ends of the input stage circuit.The negative capacitance circuit is electrically connected to the outputends of the pre-drive circuit. The output stage circuit is electricallyconnected to the out put ends of the pre-drive circuit. The input endsof the active reverse termination circuit are electrically connected tothe input ends of the output stage circuit, and the output ends of theactive reverse termination circuit are electrically connected to theoutput ends of the output stage circuit.

A pair of voltage signals V_(IP), V_(IN) are applied to the input stagecircuit which amplifies these input signals to a pair of output voltagesignals V_(IIP), V_(IIN). Then the voltage signals V_(IIP), V_(IIN) areamplified by the pre-drive circuit to a pair of voltage signals V₊, V⁻to the output stage circuit, and finally, a pair of modulated currentsignals I_(OP), I_(ON) are generated by the output stage circuit. Inaddition, the negative capacitance circuit generates a negativecapacitor to reduce the input capacitance of the output stage circuit.

Referring to FIG. 2, the input stage circuit is used for inputting thevoltage signals V_(IP), V_(IN), then matching and adjusting the voltagesignals V_(IP), V_(IN) into a pair of voltage signals V_(IIP), V_(IIN).The input stage circuit includes a transistor M_(D), a pair oftransistors M_(1A), M_(1B), and a plurality of resistors R_(INA),R_(INB), R_(1A), R_(1B). The gate and drain of the transistor M_(D) isconnected to the voltage source V_(DD). The gates of the transistorsM_(1A), M_(1B) respectively are used as the input ends of the inputstage circuit, the drains of transistors M_(1A), M_(1B) are electricallyconnected to input ends of the pre-drive circuit. The gates of thetransistors M_(1A), M_(1B) receive the voltage signals V_(IP), V_(IN),respectively, the output voltage signals V_(IIP) and V_(IIN) are takenat the drains of the transistors M_(1A), M_(1B), respectively. Thesources of these transistors are connected to a tail current source I₁.

One end of the resistor R_(INA) is connected to a voltage source V_(CM),the other end of the resistor R_(INA) is connected to the gate of thetransistor M_(1A), one end of the resistor R_(INB) is connected to thevoltage source V_(CM), the other end of the resistor R_(INB) isconnected to the gate of the transistor M_(1B); one end of the resistorR_(1A) is connected to the drain of the transistors M_(1A), the otherend of the resistor R_(1A) is connected to the source of the transistorM_(D); one end of the resistor R_(1B) is connected to the drain of thetransistors M_(1B), the other end of the resistor R_(1B) is connected tothe source of the transistor M_(D).

In this embodiment, both of the resistors, R_(INA) and R_(INB), are 50ohms. The diode-connected transistor M_(D) is used to adjust thecommon-mode output voltage to be suitable for the subsequent stage. Thepre-drive circuit is used for amplifying the voltage signals V_(IIP),V_(IIN) to output the voltage signals V₊, V⁻.

The pre-drive circuit includes a pair of transistors M_(2A), M_(2B) anda pair of resistors R_(2A), R_(2B). The gates of the transistors M_(2A),M_(2B) receive the voltage signals V_(IIP), V_(IIN), respectively, thedrains of the transistors M_(2A), M_(2B) represent the output voltagesignals V₊, V⁻, respectively. The sources of the transistors M_(2A),M_(2B) are connected together to a tail current source I₂. One end ofthe resistors R_(2A) is connected to the drain of the transistorsM_(2A), one end of the resistors R_(2B) is connected to the drain of thetransistors M_(2B), the other ends of the resistors R_(2A), R_(2B) areconnected to the voltage source V_(DD). The diode-connected transistorM_(D) is used to adjust the output common-mode voltage of the inputstage circuit, such that the transistors M_(2A), M_(2B) operate in thesaturation region during switching.

Both ends of the negative capacitance circuit are connected to the twooutput terminals of the pre-drive circuit V₊, V⁻. The negativecapacitance circuit includes a pair of transistors M_(3A), M_(3B) and acapacitor C_(c). The gates of the transistors M_(3A), M_(3B) receive thevoltage signals V₊, V⁻ respectively, the drains of transistors M_(3A)and M_(3B) are connected to the voltage signals V⁻, V₊, respectively,and the sources of the transistors M_(3A), M_(3B) are connected to apair of tail current sources I_(3A), I_(3B). The gate of the transistorsM_(3A) and the drain of the transistors M_(3B) are electricallyconnected together to the positive output end of the pre-drive circuit,the gate of the transistors M_(3B) and the drain of the transistorsM_(3A) are electrically connected together to the negative output end ofthe pre-drive circuit. Two ends of the capacitor C_(c) are connected tothe tail current sources I_(3A), I_(3B). The cross-coupled transistorsM_(3A), M_(3B) and the capacitor C_(c) can generate a negativecapacitance at the output end of the pre-drive circuit, which can reducethe capacitance at the interface between the pre-driver and outputdriver, increasing the circuit bandwidth and speed.

The output stage circuit is used for receiving the voltage signals V₊,V⁻, then outputting the modulated current signals I_(OP), I_(ON). Thenegative capacitance circuit generates a negative capacitor to reducethe input capacitance of the output stage circuit. The output stagecircuit includes a pair of transistors M_(4A), M_(4B), and a pair oftransistors M_(CA), M_(CB). The sources of the transistors M_(4A),M_(4B) are connected together to a tail current source I_(M1), thedrains of the transistors M_(4A), M_(4B) are connected to the outputends of the current signals I_(OP), I_(ON), respectively. The gate ofthe transistor M_(4A) receives the voltage signal V₊, and the gate ofthe transistor M_(4B) receives the voltage signal V⁻. The source anddrain of the transistor M_(CA) are connected together to the output endof the current signal I_(ON), and the source and drain of the transistorM_(CB) are connected together to the output end of the current signalI_(OP). The gate of the transistor M_(CA) receives the voltage signalV₊, and the gate of the transistor M_(CB) receives the voltage signalV⁻. The transistors M_(CA), M_(CB) can form an NMOS capacitor, reducingthe Miller effect of transistors M_(4A), M_(4B).

Referring to FIG. 3, the active reverse termination circuit includes apair of transistors M_(5A), M_(5B), a pair of transistors M_(6A),M_(6B), a pair of transistors M_(7A), M_(7B), a pair of transistorsM_(S1), M_(S2), a pair of resistors R_(3A), R_(3B), and a pair ofcapacitors C₁, C₂. The gate of the transistor M_(5A) is electricallyconnected to the positive output end of the pre-drive circuit, the gateof the transistor M_(5B) is electrically connected to the negativeoutput end of the pre-drive circuit. In this embodiment, the gate of thetransistor M_(5A) receives the voltage signal V₊, the gate of thetransistors M_(5B) receives the voltage signal V⁻. The sources of thetransistors M_(5A), M_(5B) are connected to a tail current sourceI_(M1)/k. The gate of the transistor M_(6A) is electrically connected tothe positive output end of the pre-drive circuit, the gate of thetransistor M_(6B) is electrically connected to the negative output endof the pre-drive circuit. The gate of the transistor M_(6A) receives thevoltage signal V₊, the gate of the transistors M_(6B) receives thevoltage signal V⁻. The sources of the transistors M_(6A), M_(6B) areconnected to a tail current source I_(M2)/k. The gate of the transistorM_(7A) is electrically connected to the positive output end of thepre-drive circuit, the gate of the transistor M_(7B) is electricallyconnected to the negative output end of the pre-drive circuit. The gateof the transistor M_(7A) receives the voltage signal V₊, the gate of thetransistors M_(7B) receives the voltage signal V⁻. The sources of thetransistors M_(7A), M_(7B) are connected to a tail current sourceI_(M3)/k.

The drains of the transistors M_(5A), M_(6A), M_(7A) are connected tothe gate of the transistor M_(S2), the drains of the transistors M_(5B),M_(6B), M_(7B) are connected to the gate of the transistor M_(S1). Thesource of the transistor M_(S1) is connected to a tail current sourceI_(B1), the source of the transistor M_(S2) is connected to a tailcurrent source I_(B2). One end of the resistors R_(3A), R_(3B) isconnected with the drains of the transistors M_(S1), M_(S2) to a supplyvoltage V_(DD). The other ends of the resistors R_(3A) and R_(3b) areconnected to the gates of the M_(S2) and M_(S1), respectively. One endof the capacitor C₁ is electrically connected to the source of thetransistor M_(S2), the other end of capacitor C₁ is directly connectedto the output current terminal I_(OP); one end of the capacitor C₂ iselectrically connected to the source of the transistor M_(S1), the otherend of capacitor C₂ is directly connected to the output terminal I_(ON).

In this embodiment, the transistors M_(S1), M_(S2) form source followerstages with low output impedance, about 20Ω, which helps to absorbreflected waves from the laser side. The active reverse back terminationcircuit is AC coupled to the output terminals of the driver circuitusing C₁ and C₂. The AC coupling technique isolates the DC voltage ofthe active reverse circuit and the driver circuit. Therefore, the activereverse termination circuit will not sink or source any excess DCcurrent from or to the output driver. There is no need to use anadditional dc offset cancellation circuit to save power and area.Meanwhile, the output stage circuit does not need to use terminalresistors to absorb reflected waves, thus greatly reducing powerconsumption.

As described above, the voltage signals V_(IIP), V_(IIN) are matched andadjusted by the input stage circuit, and then amplified by the pre-drivecircuit to the output stage circuits. Finally, the output modulatedcurrent signals I_(OP), I_(ON) are generated. The negative capacitancecircuit is used for reducing the input capacitance of the output stagecircuit. The active reverse termination circuit absorbs the reflectedwave caused by the output mismatch. There is no terminal resistance inthe output stage circuit, so the power consumption of the circuit ismuch lower than that of the traditional circuit.

Second Embodiment

Referring to FIG. 1, a laser driver with high-speed and high-current isshown. The laser driver with high-speed and high-current of the presentinvention includes an input stage circuit, a pre-drive circuit, anegative capacitance circuit, a three parallel-connected output stagescircuit and an active reverse termination circuit. A pair of voltagesignals V_(IP), V_(IN) are applied to the input stage circuit whichamplifies these input signals to a pair of output voltage signalsV_(IIP), V_(IIN). Then the voltage signals V_(IIP), V_(IIN) areamplified by the pre-drive circuit to a pair of voltage signals V₊, V⁻to the output stage circuit, and finally, a pair of modulated currentsignals I_(OP), I_(ON) are generated by the output stage circuit. Inaddition, the negative capacitance circuit generates a negativecapacitor to reduce the input capacitance of the output stage circuit.

Referring to FIG. 2 again, the input stage circuit is used for inputtingthe voltage signals V_(IP), V_(IN), then matching and adjusting thevoltage signals V_(IP), V_(IN) into a pair of voltage signals V_(IIP),V_(IIN). The input stage circuit includes a transistor M_(D), a pair oftransistors M_(1A), M_(1B), and a plurality of resistors R_(INA),R_(INB), R_(1A), R_(1B). The gate and drain of the transistor M_(D) isconnected to the voltage source V_(DD). The gates of the transistorsM_(1A), M_(1B) receive the voltage signals V_(IP), V_(IN), respectively,the output voltage signals V_(IIP) and V_(IIN) are taken at the drainsof the transistors M_(1A), M_(1B), respectively. The sources of thesetransistors are connected to a tail current source I₁. One end of theresistor R_(INA) is connected to a voltage source V_(CM), the other endof the resistor R_(INA) is connected to the gate of the transistorM_(1A); one end of the resistor R_(INB) is connected to the voltagesource V_(CM), the other end of the resistor R_(INB) is connected to thegate of the transistor M_(1B); one end of the resistor R_(1A) isconnected to the drain of the transistors M_(1A), the other end of theresistor R_(1A) is connected to the source of the transistor M_(D); oneend of the resistor R_(1B) is connected to the drain of the transistorsM_(1B), the other end of the resistor R_(1B) is connected to the sourceof the transistor M_(D).

In this embodiment, both of the resistors, R_(INA) and R_(INB), are 50ohms. The diode-connected transistor M_(D) is used to adjust thecommon-mode output voltage to be suitable for the subsequent stage. Thepre-drive circuit is used for amplifying the voltage signals V_(IIP),V_(IIN) to output the voltage signals V₊, V⁻. The pre-drive circuitincludes a pair of transistors M_(2A), M_(2B) and a pair of resistorsR_(2A), R_(2B). The gates of the transistors M_(2A), M_(2B) receive thevoltage signals V_(IIP), V_(IIN), respectively, the drains of thetransistors M_(2A), M_(2B) represent the output voltage signals V₊, V⁻,respectively. The sources of the transistors M_(2A), M_(2B) areconnected together to a tail current source I₂. One end of the resistorsR_(2A) is connected to the drain of the transistors M_(2A), one end ofthe resistors R_(2B) is connected to the drain of the transistorsM_(2B), the other ends of the resistors R_(2A), R_(2B) are connected tothe voltage source V_(DD). The diode-connected transistor M_(D) is usedto adjust the output common-mode voltage of the input stage circuit,such that the transistors M_(2A), M_(2B) operate in the saturationregion during switching. Both ends of the negative capacitance circuitare connected to the two output terminals of the pre-drive circuit V₊,V⁻. The negative capacitance circuit includes a pair of transistorsM_(3A), M_(3B) and a capacitor C_(c). The gates of the transistorsM_(3A), M_(3B) receive the voltage signals V₊, V⁻, respectively, thedrains of M_(3A) and M_(3B) are connected to the voltage signals V⁻, V₊,respectively, and the sources of the transistors M_(3A), M_(3B) areconnected to a pair of tail current sources I_(3A), I_(3B). Two ends ofthe capacitor C_(c) are connected to the tail current sources I_(3A),I_(3B). The cross-coupled transistors M_(3A), M_(3B) and the capacitorC_(c) can generate a negative capacitance at the output end of thepre-drive circuit, which can reduce the capacitance at the interfacebetween the pre-driver and output driver, increasing the circuitbandwidth and speed.

The output stage circuits are used for receiving the voltage signals V₊,V⁻, then outputting the modulated current signals I_(OP), I_(ON). Thenegative capacitance circuit generates a negative capacitor to reducethe input capacitance of the output stage circuit. The output stagecircuit includes a pair of transistors M_(4A), M_(4B), and a pair oftransistors M_(CA), M_(CB). The sources of the transistors M_(4A),M_(4B) are connected together to a tail current source I_(M1), thedrains of the transistors M_(4A), M_(4B) are connected to the outputends of the current signals I_(OP), I_(ON), respectively. The gate ofthe transistor M_(4A) receives the voltage signal V₊, and the gate ofthe transistor M_(4B) receives the voltage signal V⁻. The source anddrain of the transistor M_(CA) are connected together to the output endof the current signal I_(ON), and the source and drain of the transistorM_(CB) are connected together to the output end of the current signalI_(OP). The gate of the transistor M_(CA) receives the voltage signalV₊, and the gate of the transistor M_(CB) receives the voltage signalV⁻. The transistors M_(CA), M_(CB) can form an NMOS capacitor, reducingthe Miller effect of transistors M_(4A), M_(4B).

In this embodiment, the first output stage is directly connected to theoutput of the pre-driver circuit while the second and the third outputstages are connected to the output of the pre-driver using switchingcircuits. Each switching circuit includes a pair of transistors M_(S3),M_(S4); the gates of the transistors M_(S3), M_(S4) receive a controlsignal V_(s), the sources of the transistors M_(S3), M_(S4) areconnected to the inputs of the second output stage, the drains of thetransistors M_(S3), M_(S4) receive the voltage signals V₊, V⁻,respectively.

In addition, the number of the output stage circuits is three, and thenumber of the switching circuits is two. The internal structures ofthese output stage circuits are the same, and the internal structures ofthe two switching circuits are the same. One of the witching circuits iscontrolled by a control signal V_(s1), and the other switching circuitis controlled by a control signal V_(s2). When the control signalsV_(s1), V_(s2) are 0, the output modulation current can be adjusted from10 mA to 50 mA; when the switch control signal V_(s1) is 1 and theswitch control signal V_(s2) is 0, the output modulation current canreach 100 mA; when the switch control signals V_(s1), V_(s2) are 1, theoutput modulation current is as high as 150 mA.

Referring to FIG. 3 again, the active reverse termination circuitincludes a pair of transistors M_(5A), M_(5B), a pair of transistorsM_(6A), M_(6B), a pair of transistors M_(7A), M_(7B), a pair oftransistors M_(S1), M_(S2), a pair of resistors R_(3A), R_(3B) and apair of capacitors C₁, C₂. The gate of the transistor M_(5A) receivesthe voltage signal V₊, the gate of the transistors M_(5B) receives thevoltage signal V⁻. The sources of the transistors M_(5A), M_(5B) areconnected to a tail current source I_(M1)/k. The gate of the transistorM_(6A) receives the voltage signal V₊, the gate of the transistorsM_(6B) receives the voltage signal V⁻. The sources of the transistorsM_(6A), M_(6B) are connected to a tail current source I_(M2)/k. The gateof the transistor M_(7A) receives the voltage signal V₊, the gate of thetransistors M_(7B) receives the voltage signal V⁻. The sources of thetransistors M_(7A), M_(7B) are connected to a tail current sourceI_(M3)/k.

The drains of the transistors M_(5A), M_(6A), M_(7A) are connected tothe gate of the transistor M_(S2), the drains of the transistors M_(5B),M_(6B), M_(7B) are connected to the gate of the transistor M_(S1). Thesource of the transistor M_(S1) is connected to a tail current sourceI_(B1), the source of the transistor M_(S2) is connected to a tailcurrent source I_(B2). One end of the resistors R_(3A), R_(3B) isconnected with the drains of the transistors M_(S1), M_(S2) to a supplyvoltage V_(DD). The other ends of the resistors R_(3A) and R_(3b) areconnected to the gates of the M_(S2) and M_(S1), respectively. One endof the capacitor C₁ is electrically connected to the source of thetransistor M_(S2), the other end of capacitor C₁ is directly connectedto the output current terminal I_(OP); one end of the capacitor C₂ iselectrically connected to the source of the transistor M_(S1), the otherend of capacitor C₂ is directly connected to the output terminal I_(ON).The active reverse termination circuit absorbs reflection waves due tooutput mismatch through the capacitors C₁, C₂.

In this embodiment, the transistors M_(S1), M_(S2) form source followerstages with low output impedance, about 20Ω, which helps to absorbreflected waves from the laser side. The active reverse back terminationcircuit is AC coupled to the output terminals of the driver circuitusing C₁ and C₂. The AC coupling technique isolates the DC voltage ofthe active reverse circuit and the driver circuit. Therefore, the activereverse termination circuit will not sink or source any excess DCcurrent from or to the output driver. There is no need to use anadditional dc offset cancellation circuit which helps to save power andarea. Meanwhile, the output stage circuit does not need to use terminalresistors to absorb reflected waves, thus greatly reducing powerconsumption.

As described above, the voltage signals V_(IIP), V_(IIN) are matched andadjusted by the input stage circuit, and then amplified by the pre-drivecircuit to the output stage circuits. Finally, the output modulatedcurrent signals I_(OP), I_(ON) are generated. The negative capacitancecircuit is used for reducing the input capacitance of the output stagecircuits. The active reverse termination circuit absorbs the reflectedwave caused by the output mismatch. There is no terminal resistance inthe output stage circuit, so the power consumption of the circuit ismuch lower than that of the traditional circuit.

Third Embodiment

An integrated circuit is shown as an embodiment, and the integratedcircuit is encapsulated by a laser driver with high-speed andhigh-current. The pins of the integrated circuit include a pair of inputpins, a pair of output pins, a plurality of tail current source pins anda plurality of voltage source pins.

The input pins are used for transmitting the voltage signals V_(IP),V_(IN) to the input stage circuit. The output pins represent the outputmodulation current to the laser diode I_(OP), I_(ON). The tail currentsource pins are used for accessing the tail current sources required bythe driving circuit. The tail current sources include the sources I₁,I₂, I_(3A), I_(3B), I_(M1)/k, I_(M2)/k, I_(M3)/k, I_(B1), I_(B2) andthree I_(M1). The voltage source pins are used for accessing the voltagesources (such as V_(DD) and V_(CM)) required by the driving circuit.

Fourth Embodiment

An integrated circuit is shown as an embodiment, and the integratedcircuit is encapsulated by a laser driver with high-speed andhigh-current. The pins of the integrated circuit include a pair of inputpins, a pair of output pins, a plurality of tail current source pins, aplurality of voltage source pins, and at least one control signal pin.

The input pins are used for transmitting the voltage signals V_(IP),V_(IN) to the input stage circuit. The output pins represent the outputmodulation current to the laser diode I_(OP), I_(ON). The tail currentsource pins are used for accessing the tail current sources required bythe driving circuit. The tail current sources include the sources I₁,I₂, I_(3A), I_(3B), I_(M1)/k, I_(M2)/k, I_(M3)/k, I_(B1), I_(B2) andthree I_(M1). The voltage source pins are used for accessing the voltagesources (such as V_(DD) and V_(CM)) required by the driving circuit.While the invention has been described in terms of what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention needs not to be limited to thedisclosed embodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

What is claimed is:
 1. A laser driver with high-speed and high-current,comprising: an input stage circuit; a pre-drive circuit, beingelectrically connected to the out put ends of the input stage circuit; afully differential negative capacitance circuit, being electricallyconnected to the output ends of the pre-drive circuit; a output stagecircuit being electrically connected to the out put ends of thepre-drive circuit; and an active reverse termination circuit; the inputends of the active reverse termination circuit being electricallyconnected to the input ends of the output stage circuit, and the outputends of the active reverse termination circuit being electricallyconnected to the output ends of the output stage circuit.
 2. The laserdriver according to claim 1, wherein the active reverse terminationcircuit comprises: a pair of transistors M_(5A), M_(5B); the gate of thetransistor M_(5A) is electrically connected to the positive output endof the pre-drive circuit, the gate of the transistor M_(5B) iselectrically connected to the negative output end of the pre-drivecircuit; the sources of the transistors M_(5A), M_(5B) are electricallyconnected to a tail current source I_(M1)/k; a pair of transistorsM_(6A), M_(6B); the gate of the transistor M_(6A) is electricallyconnected to the positive output end of the pre-drive circuit, the gateof the transistor M_(6B) is electrically connected to the negativeoutput end of the pre-drive circuit; the sources of the transistorsM_(6A); M_(6B) are electrically connected to a tail current sourceI_(M2)/k; a pair of transistors M_(7A), M_(7B); the gate of thetransistor M_(7A) is electrically connected to the positive output endof the pre-drive circuit, the gate of the transistor M_(7B) iselectrically connected to the negative output end of the pre-drivecircuit; the sources of the transistors M_(7A), M_(7B) are electricallyconnected to a tail current source I_(M3)/k; a pair of transistorsM_(S1), M_(S2); the drains of the transistors M_(5A), M_(6A), M_(7A) areelectrically connected to the gate of the transistor M_(S2), the drainsof the transistors M_(5B), M_(6B), M_(7B) are electrically connected tothe gate of the transistor M_(S1); the source of the transistor M_(S1)is electrically connected to a tail current source I_(B1), the source ofthe transistor M_(S2) is electrically connected to a tail current sourceI_(B2); a pair of resistors R_(3A), R_(3B); one end of these resistorsis connected with the drains of the transistors M_(S1), M_(S2) to asupply voltage V_(DD); the other ends of the resistors R_(3A) and R_(3b)are connected to the gates of the M_(S2) and M_(S1), respectively; and apair of capacitors C₁, C₂; one end of the capacitor C₁ is electricallyconnected to the source of the transistor M_(S2), the other end ofcapacitor C₁ is directly connected to a output current terminal I_(OP);one end of the capacitor C₂ is electrically connected to the source ofthe transistor M_(S1), the other end of capacitor C₂ is directlyconnected to a output terminal I_(ON).
 3. The laser driver according toclaim 2, wherein the input stage circuit comprises: a transistor M_(D);the gate and drain of the transistor M_(D) are electrically connected tothe voltage source V_(DD); a pair of transistors M_(1A), M_(1B); thegates of the transistors M_(1A), M_(1B) respectively are used as theinput ends of the input stage circuit, the drains of transistors M_(1A),M_(1B) are electrically connected to input ends of the pre-drivecircuit, the sources of the M_(1A) and M_(1B) are connected to a tailcurrent source I₁; and a plurality of resistors R_(INA), R_(INB),R_(1A), and R_(1B); one end of the resistor R_(INA) is electricallyconnected to a voltage source V_(CM), the other end of the resistorR_(INA) is electrically connected to the gate of the transistor M_(1A);one end of the resistor R_(INB) is electrically connected to the voltagesource V_(CM), the other end of the resistor R_(INB) is electricallyconnected to the gate of the transistor M_(1B); one end of the resistorR_(1A) is electrically connected to the drain of the transistors M_(1A),the other end of the resistor R_(1A) is electrically connected to thesource of the transistor M_(D); one end of the resistor R_(1B) iselectrically connected to the drain of the transistors M_(1B), the otherend of the resistor R_(1B) is electrically connected to the source ofthe transistor M_(D).
 4. The laser driver according to claim 3, whereinboth resistors R_(INA) and R_(INB) are 50 ohms.
 5. The laser driveraccording to claim 3, wherein the pre-drive circuit comprises: a pair oftransistors M_(2A), M_(2B); the gates of the transistors M_(2A), M_(2B)are electrically connected to the drains of transistors M_(1A), M_(1B)respectively, the drains of the transistors M_(2A), M_(2B) areelectrically connected to input ends of the output stage circuit, thesources of the transistors M_(2A), M_(2B) are connected to a tailcurrent source I₂; and a pair of resistors R_(2A), R_(2B); one end ofthe resistors R_(2A) is connected to the drain of the transistorsM_(2A), one end of the resistors R_(2B) is connected to the drain of thetransistors M_(2B), the other ends of the resistors R_(2A), R_(2B) areconnected to the voltage source V_(DD).
 6. The laser driver according toclaim 5, wherein the negative capacitance circuit comprises: a pair oftransistors M_(3A), M_(3B); the gate of the transistors M_(3A) and thedrain of the transistors M_(3B) are electrically connected together tothe positive output end of the pre-drive circuit, the gate of thetransistors M_(3B) and the drain of the transistors M_(3A) areelectrically connected together to the negative output end of thepre-drive circuit, the sources of the transistors M_(3A), M_(3B) areconnected to a pair of tail current sources I_(3A), I_(3B) respectively;and a capacitor C_(c); two ends of the capacitor C_(c) are connected tothe tail current sources I_(3A), I_(3B).
 7. The laser driver accordingto claim 6, wherein the output stage circuit comprises: a pair oftransistors M_(4A), M_(4B); the sources of the transistors M_(4A),M_(4B) are electrically connected together to a tail current sourceI_(M1), the drains of the transistors M_(4A), M_(4B) represent theoutput ends of output current terminals I_(OP), I_(ON); the gate of thetransistor M_(4A) is electrically connected to the positive output endof the pre-drive circuit, and the gate of the transistor M_(4B) iselectrically connected to the negative output end of the pre-drivecircuit; and a pair of transistors M_(CA), M_(CB); the source and drainof the transistor M_(CA) are connected together to the output end of theoutput current terminal I_(ON), and the source and drain of thetransistor M_(CB) are connected together to the output end of the outputcurrent terminal I_(OP); the gate of the transistor M_(CA) iselectrically connected to the positive output end of the pre-drivecircuit, and the gate of the transistor M_(CB) is electrically connectedto the negative output end of the pre-drive circuit.
 8. The laser driveraccording to claim 1, wherein the output stage circuit is a threeparallel connected output stages circuit.
 9. The laser driver accordingto claim 8, wherein the first output stage is directly connected to theoutput of the pre-drive circuit while the second and the third outputstages are connected to the output of pre-drive using switchingcircuits.
 10. The laser driver according to claim 9, wherein eachswitching circuit comprises: a pair of transistors M_(S3), M_(S4); thegates of the transistors M_(S3), M_(S4) receive a switch control signalV_(s), the sources of the transistors M_(S3), M_(S4) respectivelyelectrically are connected to the inputs of the second output stage twoinput ends of the corresponding switching circuit, the drains of thetransistors M_(S3), M_(S4) are electrically connected to the output endsof the pre-drive circuit respectively.
 11. The laser driver according toclaim 9, wherein one of the witching circuits is controlled by a switchcontrol signal V_(s1), and the other of the switching circuits iscontrolled by a switch control signal V_(s2).
 12. The laser driveraccording to claim 11, wherein when the switch control signals V_(s1),V_(s2) are 0, the output modulation current can be adjusted from 10 mAto 50 mA; when the switch control signal V_(s1) is 1 and the switchcontrol signal V_(s2) is 0, the output modulation current can reach 100mA; when the switch control signals V_(s1), V_(s2) are 1, the outputmodulation current is as high as 150 mA.
 13. A laser driver withhigh-speed and high-current, comprising: an input stage circuit whichreceives a pair of fully differential input voltage signals, V_(IP),V_(IN), then, adjusting the common-mode output voltage of signalsV_(IIP), V_(IIN), such that they could be applied to the subsequentstage; a pre-drive circuit, for amplifying the voltage signals V_(IIP),V_(IIN) to a pair of voltage signals V₊, V⁻; a fully differentialnegative capacitance circuit that is directly connected to the outputterminals of the pre-driver circuit, V₊, V⁻; the negative capacitancecircuit generates a negative capacitor to reduce the input capacitanceof the output stage circuit; an output stage circuit, for receiving thevoltage signals V₊, V⁻, then outputting a pair of modulated currentsignals I_(OP), I_(ON); and an active reverse termination circuit, forabsorbing the reflected wave caused by the output mismatch of the outputstage circuit.
 14. The laser driver according to claim 13, wherein theactive reverse termination circuit comprises: a pair of transistorsM_(5A), M_(5B); the gate of the transistor M_(5A) receives the voltagesignal V₊, the gate of the transistors M_(5B) receives the voltagesignal V⁻; the sources of the transistors M_(5A), M_(5B) areelectrically connected to a tail current source I_(M1)/k; a pair oftransistors M_(6A), M_(6B); the gate of the transistor M_(6A) receivesthe voltage signal V₊, the gate of the transistors M_(6B) receives thevoltage signal V⁻; the sources of the transistors M_(6A); M_(6B) areelectrically connected to a tail current source I_(M2)/k; a pair oftransistors M_(7A), M_(7B); the gate of the transistor M_(7A) receivesthe voltage signal V₊, the gate of the transistors M_(7B) receives thevoltage signal V⁻; the sources of the transistors M_(7A), M_(7B) areelectrically connected to a tail current source I_(M3)/k; a pair oftransistors M_(S1), M_(S2); the drains of the transistors M_(5A),M_(6A), M_(7A) are electrically connected to the gate of the transistorM_(S2), the drains of the transistors M_(5B), M_(6B), M_(7B) areelectrically connected to the gate of the transistor M_(S1); the sourceof the transistor M_(S1) is electrically connected to a tail currentsource I_(B1), the source of the transistor M_(S2) is electricallyconnected to a tail current source I_(B2); a pair of resistors R_(3A),R_(3B); one end of these resistors is connected with the drains of thetransistors M_(S1), M_(S2) to a supply voltage V_(DD); the other ends ofthe resistors R_(3A) and R_(3b) are connected to the gates of the M_(S2)and M_(S1) respectively; and a pair of capacitors C₁, C₂; one end of thecapacitor C₁ is electrically connected to the source of the transistorM_(S2), the other end of capacitor C₁ is directly connected to theoutput current terminal I_(OP); one end of the capacitor C₂ iselectrically connected to the source of the transistor M_(S1), the otherend of capacitor C₂ is directly connected to the output terminal I_(ON).15. The laser driver according to claim 14, wherein the input stagecircuit comprises: a transistor M_(D); the gate and drain of thetransistor M_(D) are electrically connected to the voltage sourceV_(DD); a pair of transistors M_(1A), M_(1B); the gates of thetransistors M_(1A), M₁, respectively receive the voltage signals V_(IP),V_(IN), the output voltage signals V_(IIP) and V_(IIN) are taken at thedrains of M_(1A), M_(1B) respectively, the sources of the M_(1A) andM_(1B) are connected to a tail current source I₁; and a plurality ofresistors R_(INA), R_(INB), R_(1A), and R_(1B); one end of the resistorR_(INA) is connected to a voltage source V_(CM), the other end of theresistor R_(INA) is connected to the gate of the transistor M_(1A); oneend of the resistor R_(INA) is connected to the voltage source V_(CM),the other end of the resistor R_(INB) is connected to the gate of thetransistor M_(1B); one end of the resistor R_(1A) is connected to thedrain of the transistors M_(1A), the other end of the resistor R_(1A) isconnected to the source of the transistor M_(D); one end of the resistorR_(1B) is connected to the drain of the transistors M_(1B), the otherend of the resistor R_(1B) is connected to the source of the transistorM_(D).
 16. The laser driver according to claim 15, wherein the pre-drivecircuit comprises: a pair of transistors M_(2A), M_(2B); the gates ofthe transistors M_(2A), M_(2B) receive the voltage signals V_(IIP),V_(IIN) respectively, the drains of the transistors M_(2A), M_(2B)represent the output voltage signals V₊, V⁻ respectively, the sources ofthe transistors M_(2A), M_(2B) are connected to a tail current sourceI₂; and a pair of resistors R_(2A), R_(2B); one end of the resistorsR_(2A) is connected to the drain of the transistors M_(2A), one end ofthe resistors R_(2B) is connected to the drain of the transistorsM_(2B), the other ends of the resistors R_(2A), R_(2B) are electricallyconnected to the voltage source V_(DD).
 17. The laser driver accordingto claim 16, wherein the negative capacitance circuit comprises: a pairof transistors M_(3A), M_(3B); the gates of the transistors M_(3A),M_(3B) receive the voltage signals V₊, V⁻, the drains of M_(3A) andM_(3B) receive the voltage signals V⁻, V₊ respectively, the sources ofthe transistors M_(3A), M_(3B) are electrically connected to a pair oftail current sources I_(3A), I_(3B) respectively; and a capacitor C_(c);two ends of the capacitor C_(c) are electrically connected to the tailcurrent sources I_(3A), I_(3B).
 18. The laser driver according to claim17, wherein the output stage circuit comprises: a pair of transistorsM_(4A), M_(4B); the sources of the transistors M_(4A), M_(4B) areconnected together to a tail current source I_(M1), the drains of thetransistors M_(4A), M_(4B) represent the output ends of the currentsignals I_(OP), I_(ON); the gate of the transistor M_(4A) receives thevoltage signal V₊, and the gate of the transistor M_(4B) receives thevoltage signal V⁻; and a pair of transistors M_(CA), M_(CB); the sourceand drain of the transistor M_(CA) are connected together to the outputend of the current signal I_(ON), and the source and drain of thetransistor M_(CB) are connected together to the output end of thecurrent signal I_(OP); the gate of the transistor M_(CA) receives thevoltage signal V₊, and the gate of the transistor M_(CB) receives thevoltage signal V⁻.
 19. An integrated circuit, being encapsulated by alaser driver with high-speed and high-current; the laser drivercomprising: an input stage circuit which receives a pair of fullydifferential input voltage signals, V_(IP), V_(IN), then, adjusting thecommon-mode output voltage of signals V_(IIP), V_(IIN), such that theycould be applied to the subsequent stage; a pre-drive circuit, foramplifying the voltage signals V_(IIP), V_(IIN) to a pair of voltagesignals V₊, V⁻; a fully differential negative capacitance circuit thatis directly connected to the output terminals of the pre-driver circuit,V₊, V⁻; the negative capacitance circuit generates a negative capacitorto reduce the input capacitance of the output stage circuit; an outputstage circuit, for receiving the voltage signals V₊, V⁻, then outputtinga pair of modulated current signals I_(OP), I_(ON); and an activereverse termination circuit, for absorbing the reflected wave caused bythe output mismatch of the output stage circuit; wherein the activereverse termination circuit comprises: a pair of transistors M_(5A),M_(5B); the gate of the transistor M_(5A) receives the voltage signalV₊, the gate of the transistors M_(5B) receives the voltage signal V⁻;the sources of the transistors M_(5A), M_(5B) are electrically connectedto a tail current source I_(M1)/k; a pair of transistors M_(6A), M_(6B);the gate of the transistor M_(6A) receives the voltage signal V₊, thegate of the transistors M_(6B) receives the voltage signal V⁻; thesources of the transistors M_(6A), M_(6B) are electrically connected toa tail current source I_(M2)/k; a pair of transistors M_(7A), M_(7B);the gate of the transistor M_(7A) receives the voltage signal V₊, thegate of the transistors M_(7B) receives the voltage signal V⁻; thesources of the transistors M_(7A), M_(7B) are electrically connected toa tail current source I_(M3)/k; a pair of transistors M_(S1), M_(S2);the drains of the transistors M_(5A), M_(6A), M_(7A) are electricallyconnected to the gate of the transistor M_(S2), the drains of thetransistors M_(5B), M_(6B), M_(7B) are electrically connected to thegate of the transistor M_(S1); the source of the transistor M_(S1) iselectrically connected to a tail current source I_(B1), the source ofthe transistor M_(S2) is electrically connected to a tail current sourceI_(B2); a pair of resistors R_(3A), R_(3B); one end of these resistorsis connected with the drains of the transistors M_(S1), M_(S2) to asupply voltage V_(DD); the other ends of the resistors R_(3A) and R_(3b)are connected to the gates of the M_(S2) and M_(S1) respectively; and apair of capacitors C₁, C₂; one end of the capacitor C₁ is electricallyconnected to the source of the transistor M_(S2), the other end ofcapacitor C₁ is directly connected to the output current terminalI_(OP); one end of the capacitor C₂ is electrically connected to thesource of the transistor M_(S1), the other end of capacitor C₂ isdirectly connected to the output terminal I_(ON).
 20. The integratedcircuit according to claim 19, wherein the output stage circuit is athree parallel connected output stages circuit; the first output stageis directly connected to the output of the pre-drive circuit while thesecond and the third output stages are connected to the output ofpre-drive using switching circuits; the pins of the integrated circuitcomprise: a pair of input pins, for transmitting the voltage signalsV_(IP), V_(IN) to the input stage circuit; a pair of output pins, whichrepresent the output modulation current to the laser diode; a pluralityof tail current source pins, for accessing the tail current sourcesrequired by the driving circuit of the laser driver; a plurality ofvoltage source pins, for accessing the voltage sources required by thedriving circuit of the laser driver; and two control signals pins, areused to activate the switching circuits designated for the second andthe third output driver stages.